All patients will be monitored by electrocardiography, noninvasive and invasive arterial blood pressure, pulse oximetry, capnography, fraction inspired oxygen concentration (FiO2). After preoxygenation, general anesthesia will be induced with Propofol 2 mg/kg IV, Fentanyl 2 µg/kg IV and Rocronium 0.9 mg/kg IV followed by endotracheal intubation and maintenance with a mixture of air, oxygen 50% with Desﬂurane. Mechanical ventilation will be adjusted to maintain end-tidal CO2 between 35-40 mmHg. Central venous line will be inserted for monitoring of central venous pressure (CVP) with ultrasonography guidance.